Publisher：EPJ Web of Conferences  

The role of three-nucleon forces on structure properties of nuclei is discussed within the realistic shell model. Calculations are performed by employing effective shell-model Hamiltonians derived by way of many-perturbation theory from chiral potentials including the nucleon-nucleon and three-nucleon components. A sketch of the formalism in treating the three-nucleon force is given and some selected results for f p- and pshell nuclei are shown. Particular attention is devoted to the effects of the three-nucleon force on the monopole component of the effective shell-model interaction by showing how relevant they are in correcting the monopole interaction derived from the nucleon-nucleon force only and correctly describing the formation of shell structure as well as the enhancement in the spin-orbit splitting. A decomposition scheme based on the rank of irreducible tensors forming the three-nucleon force at the next-to-next-to-leading order is also presented to recognize their impact on the spin-orbit enhancement.

DOI： 10.1051/epjconf/202430404002

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

We survey the impact of nuclear three-body forces on structure properties of nuclei within the shell model. It has long been acknowledged, since the seminal works of Zuker and coworkers, that three-body forces play a fundamental role in making the monopole component of shell-model Hamiltonians, derived from realistic nucleon–nucleon potentials, able to reproduce the observed evolution of the shell structure. In the vast majority of calculations, however, their effects have been taken into account by shell-model practitioners by introducing ad hoc modifications of the monopole matrix elements. During last twenty years, a new theoretical approach, framed within the chiral perturbation theory, has progressed in developing nuclear potentials, where two- and many-body components are naturally and consistently built in. This new class of nuclear forces allows to carry out nuclear structure studies that are improving our ability to understand nuclear phenomena in a microscopic approach. We provide in this work an update on the status of the nuclear shell model based on realistic Hamiltonians that are derived from two- and three-nucleon chiral potentials, focusing on the role of the three-body component to provide the observed shell evolution and closure properties, as well as the location of driplines. To this end, we present the results of shell-model calculations and their comparison with recent experimental measurements, which enlighten the relevance of the inclusion of three-nucleon forces to master our knowledge of the physics of atomic nuclei.

DOI： 10.1016/j.ppnp.2023.104079

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

Many-body methods that use Gaussian-wave packets to describe nucleon spatial distribution have been widely employed for depicting various phenomena in nuclear systems, in particular clustering. So far, however, the chiral effective field theory, a state-of-the-art theory of nuclear force, has not been applied to such methods. In this paper, we give the formalism to calculate the two-body matrix elements of the chiral two-nucleon forces using the Gaussian-wave packets. We also visualize the matrix elements and investigate the contributions of the central and tensor forces. This work is a foothold towards an ab initio description of various cluster phenomena in view of nucleons, pions, and many-nucleon forces.

DOI： 10.1093/ptep/ptad087

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Other Link： https://academic.oup.com/ptep/article-pdf/2023/7/073D03/51004209/ptad087.pdf

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Sociedad Mexicana de Fisica A C  

The correlation functions of pΞ − and ΛΛ pairs from high-energy pp collisions are investigated in the coupled-channel formalism. The NΞΛΛ coupled-channel potentials obtained in the lattice QCD calculation at almost physical quark masses are employed. The pΞ − correlation function shows the large enhancement from the pure Coulomb case, while the ΛΛ correlation function shows the moderate enhancement from the pure quantum statistics case. This agreement indicates that both the NΞ and ΛΛ interactions are moderately attractive without having quasibound or bound state.

DOI： 10.31349/suplrevmexfis.3.0308124

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Publishing type：Research paper (international conference proceedings)  

The correlation functions of pΞ− and ΛΛ pairs from pp and pA collisions are studied in the coupled-channel framework using the NΞ-ΛΛ coupled-channel baryon-baryon potentials obtained in the lattice QCD calculation at almost physical quark masses. The pΞ− correlation function is calculated to be significantly enhanced from the pure Coulomb case, while the ΛΛ correlation function is slightly enhanced from that of the pure fermion quantum statistics. These features reflect the large and small scattering lengths in the pΞ− and ΛΛ channels in magnitude, and agree with the observed data by the ALICE collaboration. The agreement confirms the S = −2 baryon-baryon potentials from lattice QCD.

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

How the nuclear force behaves in cluster states, in particular those consisting of the α clusters, has been investigated so far, but not yet elucidated. Today the chiral effective field theory (EFT) is established and it would shed new light on the microscopic understanding of the cluster states. We aim to address a possible source of the attraction in the cluster states of 8Be in view of the pion exchange. Namely, we investigate whether the two-pion-exchange interaction acts as a dominant attraction in the α + α system as predicted by a previous work. We describe theoretically the cluster structure of 8Be by the Brink model, for which the effective interaction is designed from the realistic nuclear force derived through the chiral EFT. The two-body matrix elements of the chiral interaction with the local-Gaussian bases are formulated within the approximation of the spin-isospin saturation forming an α particle. Introducing a global prefactor to the chiral interaction phenomenologically, the ground and low-lying excited states of 8Be, the scattering phase shift of the α-α system as well, are satisfactorily depicted. The attraction in the cluster states is found to be stemming from the two-pion-exchange contributions dominantly, along with nonnegligible short-range terms. The present work can be the foundation towards constructing realistic cluster models, by which the cluster states will be revealed microscopically in the next step.

DOI： 10.1088/1361-6471/ac58b3

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Language：Others   Publishing type：Research paper (other academic)  

The correlation functions of pΞ− and ΛΛ pairs from pp and pA collisions are studied in the coupled-channel framework using the NΞ-ΛΛ coupled-channel baryon-baryon potentials obtained in the lattice QCD calculation at almost physical quark masses. The pΞ− correlation function is calculated to be significantly enhanced from the pure Coulomb case, while the ΛΛ correlation function is slightly enhanced from that of the pure fermion quantum statistics. These features reflect the large and small scattering lengths in the pΞ− and ΛΛ channels in magnitude, and agree with the observed data by the ALICE collaboration. The agreement confirms the S = −2 baryon-baryon potentials from lattice QCD.

Language：Others   Publishing type：Research paper (scientific journal)  

The momentum correlation functions of S=-2 baryon pairs (pΞ- and ΛΛ) produced in high-energy pp and pA collisions are investigated on the basis of the coupled-channels formalism. The strong interaction is described by the coupled-channels HAL QCD potential obtained by lattice QCD simulations near physical quark masses, while the hadronic source function is taken to be a static Gaussian form. The coupled-channels effect, the threshold difference, the realistic strong interaction, and the Coulomb interaction are fully taken into account for the first time in the femtoscopic analysis of baryon-baryon correlations. The characteristic features of the experimental data for the pΞ- and ΛΛ pairs at the Large Hadron Collider are reproduced quantitatively with a suitable choice of nonfemtoscopic parameters and the source size. The agreement between theory and experiment indicates that the NΞ (ΛΛ) interaction is moderately (weakly) attractive without having a quasibound (bound) state.

DOI： 10.1103/PhysRevC.105.014915

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The even-even Ti isotopic chain, from A=42 to 70, has been studied within the nuclear shell-model framework by employing an effective Hamiltonian which is derived by way of many-body perturbation theory from a chiral potential with two- and three-body forces, and includes three-body contributions which account for Pauli principle violations in nuclei with more than two valence particles. We consider Ca40 as a closed core and a model space spanned by the neutron and proton 0f1p orbitals with the addition of the 0g9/2 orbital for neutrons. Calculated two-neutron separation energies and excitation energies of the yrast 2+ states are reported and compared with the experimental data, which are available up to Ti62. The present study intends to investigate the effects of the adopted effective interactions on the evolution of the shell structure.

DOI： 10.1103/PhysRevC.104.054304

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Background: The C9 nucleus and related capture reaction, B8(p,γ)C9, have been intensively studied with an astrophysical interest. Due to the weakly bound nature of C9, its structure is likely to be described as the three-body (Be7+p+p). Its continuum structure is also important to describe reaction processes of C9, with which the reaction rate of the B8(p,γ)C9 process have been extracted indirectly. Purpose: We preform three-body calculations on C9 and discuss properties of its ground and low-lying states via breakup reactions. Methods: We employ the three-body model of C9 using the Gaussian-expansion method combined with the complex-scaling method. This model is implemented in the four-body version of the continuum-discretized coupled-channels method, by which breakup reactions of C9 are studied. The intrinsic spin of Be7 is disregarded. Results: By tuning a three-body interaction in the Hamiltonian of C9, we obtain the low-lying 2+ state with the resonant energy 0.781 MeV and the decay width 0.137 MeV, which is consistent with the available experimental information and a relatively high-lying second 2+ wider resonant state. Our calculation predicts also sole 0+ and three 1- resonant states. We discuss the role of these resonances in the elastic breakup cross section of C9 on Pb208 at 65 and 160 MeV/nucleon. Conclusions: The low-lying 2+ state is probed as a sharp peak of the breakup cross section, while the 1- states enhance the cross section around 3 MeV. Our calculations will further support the future and ongoing experimental campaigns for extracting astrophysical information and evaluating the two-proton removal cross sections.

DOI： 10.1103/PhysRevC.104.034612

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We employ the shell model with the chiral two- and three-nucleon forces. The effective Hamiltonian relevant to the valence-model space is computed microscopically. This framework is applied to the study of the neutron-drip line of the calcium isotopes. Our simulation shows that the calculated two-neutron separation energies are consistent with those of currently available experiment and 70Ca is possibly bound, as other theoretical attempts predict.

DOI： 10.1007/s00601-021-01655-8

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We study the momentum correlation functions of pΞ - and Λ Λ pairs produced in high-energy nuclear collisions by using the coupled-channel framework and the NΞ - Λ Λ coupled-channel baryon-baryon potentials recently obtained from lattice QCD calculations at almost physical quark masses. The calculated results are found to well describe the correlation function data from pp and pPb collisions. This agreement confirms the S= - 2 baryon-baryon potentials from lattice QCD and supports the existence of the H dibaryon as a virtual state around the NΞ threshold.

DOI： 10.1007/s00601-021-01626-z

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Background: The hadron-deuteron correlation function has attracted much interest as a potential method to access three-hadron interactions. However, the weakly bound nature of deuterons has not been considered in the preceding studies. Purpose: The breakup effect of deuterons in the deuteron-Ξ- (d-Ξ-) correlation function CdΞ- is investigated. Methods: The d-Ξ- scattering is described by a nucleon-nucleon-Ξ three-body reaction model. The continuum-discretized coupled-channels method, which is a fully quantum-mechanical and nonperturbative reaction model, is adopted. Results: CdΞ- turns out to be sensitive to the strong interaction and enhanced by the deuteron breakup effect by 6%-8% for a d-Ξ- relative momentum below about 70 MeV/c. Low-lying neutron-neutron continuum states are responsible for this enhancement. Conclusions: Within the adopted model, the deuteron breakup effect on CdΞ- is found to be appreciable but not very significant. Except for the enhancement by several percent, studies on CdΞ- without the deuteron breakup effect can be justified.

DOI： 10.1103/PhysRevC.103.065205

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We demonstrate that universal scaling behavior is observed in the current coronavirus (SARS-CoV-2) spread, the COVID-19 pandemic, in various countries. We analyze the numbers of infected people who tested positive (cases) in 11 selected countries (Japan, USA, Russia, Brazil, China, Italy, Indonesia, Spain, South Korea, UK, and Sweden). By using a double exponential function called the Gompertz function, f G (x)=exp(-e-x), the number of cases is well described as N(t)=N 0 f G(γ(t-t0)), where N0, γ, and t 0 are the final number of cases, the damping rate of the infection probability, and the peak time of the daily number of new cases, dN(t)/dt, respectively. The scaled data of cases in most of the analyzed countries are found to collapse onto a common scaling function f G(x) with x=γ(t-t_0) being the scaling variable in the range of f G(x)± 0.05. The recently proposed indicator, the so-called K value, the increasing rate of cases in one week, is also found to show universal behavior. The mechanism for the Gompertz function to appear is discussed from the time dependence of the produced pion numbers in nucleus-nucleus collisions, which is also found to be described by the Gompertz function.

DOI： 10.1093/ptep/ptaa148

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We report in this paper a study in terms of the nuclear shell model about the location of the calcium isotopes drip line. The starting point is considering the realistic two-body potential derived by Entem and Machleidt within chiral perturbation theory at next-to-next-to-next-to-leading order (N3LO), as well as a chiral three-body force at next-to-next-to-leading order (N2LO) whose structure and low-energy constants are consistent with the two-body potential. Then we construct the effective single-particle energies and residual interaction needed to diagonalize the shell-model Hamiltonian. The calculated two-neutron separation energies agree nicely with experiment until Ca56, which is the heaviest isotope whose mass has been measured, and do not show any sign of two-neutron emission until Ca70. We discuss the role of the choice of the model space in determining the neutron drip line, and also the dependence of the results on the parameters of the shell-model Hamiltonian.

DOI： 10.1103/PhysRevC.102.054326

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The possibility of the He8 and Li9 clusters in atomic nuclei is discussed. Until now most of the clusters in the conventional models have been limited to the closures of the three-dimensional harmonic oscillators, such as He4, O16, and Ca40. In the neutron-rich nuclei, however, the neutron-to-proton ratio (N/Z) is not unity, and it is worthwhile to think about more neutron-rich objects with N>Z as the building blocks of cluster structures. Here the nuclei with the neutron number six, which is the subclosure of the p3/2 subshell of the jj-coupling shell model, are assumed to be clusters, and thus we study the He8 and Li9 cluster structures in Be16 (He8+He8), B17 (He8+Li9), C18 (Li9+Li9), and C24 (He8+He8+He8). Recent progress of the antisymmetrized quasi-cluster model (AQCM) enables us to utilize jj-coupling shell-model wave functions as the clusters rather easily. It is shown that the He8+Li9 and Li9+Li9 cluster configurations cover the lowest shell-model states of B17 and C18, respectively. To predict cluster states with large relative distances, we increase the expectation value of the principal quantum numbers by adding the nodes to the lowest states under the condition that the total angular momentum is unchanged (equal to Jπ=0+). As a result, developed cluster states are obtained around the corresponding threshold energies. The rotational band structure of C24, which reflects the symmetry of equilateral triangular configuration (D3h symmetry) of three He8 clusters, also appears around the threshold energy. We suggest a novel mechanism whereby the spin-orbit interaction induces the clustering, which is distinctive of neutron-rich nuclei.

DOI： 10.1103/PhysRevC.102.024332

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Three-nucleon force and continuum play important roles in reproducing the properties of atomic nuclei around driplines. Therefore it is valuable to build up a theoretical framework where both effects can be taken into account to solve the nuclear Schrödinger equation. To this end, in this letter, we have expressed the chiral three-nucleon force within the continuum Berggren representation, so that bound, resonant and continuum states can be treated on an equal footing in the complex-momentum space. To reduce the model dimension and computational cost, the three-nucleon force is truncated at the normal-ordered two-body level and limited in the sd-shell model space, with the residual three-body term being neglected. We choose neutron-rich oxygen isotopes as the test ground because they have been well studied experimentally, with the neutron dripline determined. The calculations have been carried out within the Gamow shell model. The quality of our results in reproducing the properties of oxygen isotopes around the neutron dripline shows the relevance of the interplay between three-nucleon force and the coupling to continuum states. We also analyze the role played by the chiral three-nucleon force, by dissecting the contributions of the 2π exchange, 1π exchange and contact terms.

DOI： 10.1016/j.physletb.2020.135257

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So far, the nature of three-nucleon forces (3NFs) derived by the chiral effective field theory has been intensively investigated by various theoretical approaches. In this work, to address the chiral 3NF within the shell-model framework, three-body matrix elements are formulated in terms of the harmonic oscillator basis functions, by adopting the nonlocal regulator. We perform a benchmark test for p-shell nuclei inorder to confirm our framework. Then we show that the contribution of the 3NF to the monopole component of the effective shell model Hamiltonian plays an essential role to account for the shell evolution of f p-shell nuclei.

DOI： 10.1051/epjconf/201922301018

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We present a study of the role played by realistic three-body forces in providing a reliable monopole component of the effective shell-model Hamiltonian. To this end, starting from a nuclear potential built up within the chiral perturbation theory, we derive effective shell-model Hamiltonians with and without the contribution of the three-body potential and compare the results of shell-model calculations with a set of observables that evidence shell-evolution properties. The testing ground of our investigation is nuclei belonging to the fp shell, since the shell-evolution towards shell closures in Ca48 and Ni56 provides a paradigm for shell-model Hamiltonians. Our analysis shows that only by including contributions of the three-body force is the monopole component of the effective shell-model Hamiltonian then able to reproduce the experimental shell evolution towards and beyond the closure at N=28.

DOI： 10.1103/PhysRevC.100.034324

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We have found that, in the original paper, the calculated values listed in Table 4 and 5 [Table presented] should have been divided by a factor 9. This is due to the absence of the prefactor

DOI： 10.1016/j.nuclphysa.2019.02.005

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In nuclear structure calculations, the choice of a limited model space, due to computational needs, leads to the necessity to renormalize the Hamiltonian as well as any transition operator. Here, we present a study of the renormalization procedure and effects of the Gamow-Teller operator within the framework of the realistic shell model. Our effective shell-model operators are obtained, starting from a realistic nucleon-nucleon potential, by way of the many-body perturbation theory in order to take into account the degrees of freedom that are not explicitly included in the chosen model space. The theoretical effective shell-model Hamiltonian and transition operators are then employed in shell-model calculations, whose results are compared with data of Gamow-Teller transition strengths and double-β half-lives for nuclei which are currently of interest for the detection of the neutrinoless double-β decay process, in a mass interval ranging from A=48 up to A=136. We show that effective operators are able to reproduce quantitatively the spectroscopic and decay properties without resorting to an empirical quenching neither of the axial coupling constant gA, nor of the spin and orbital gyromagnetic factors. This should assess the reliability of applying present theoretical tools to this problematic.

DOI： 10.1103/PhysRevC.100.014316

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In this paper, we extend our previous realistic shell-model study of Gamow-Teller strengths and double-β decay properties for nuclei around 132Sn to lighter mass nuclei. The effective shell-model Hamiltonian and transition operators are microscopically derived by way of many-body perturbation theory, without resorting to empirical parameters. Our main aim is to further check the reliability of our approach and verify its stability in other mass regions. Calculated energy spectra as well as electric-quadrupole and β-decay properties are presented for 76Ge and 82Se and compared with the experimental data, together with some results for 130Te and 136Xe already reported in our previous paper. Finally, some preliminary results of nuclear matrix elements responsible for the neutrinoless double beta decay, calculated by using the bare operator, are shown.

DOI： 10.1051/epjconf/201819402007

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In atomic nuclei, the spin-orbit interaction originates from the coupling of the orbital motion of a nucleon with its intrinsic spin. Recent experimental and theoretical works have suggested a weakening of the spin-orbit interaction in neutron-rich nuclei far from stability. To study this phenomenon, we have investigated the spin-orbit energy splittings of single-hole and single-particle valence neutron orbits of 132Sn. The spectroscopic strength of single-hole states in 131Sn was determined from the measured differential cross sections of the tritons from the neutron-removing 132Sn(d, t)131Sn reaction, which was studied in inverse kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spectroscopic factors of the lowest 3/2+, 1/2+ and 5/2+ states were found to be consistent with their maximal values of (2j+1), confirming the robust N=82 shell closure at 132Sn. We compared the spin-orbit splitting of neutron single-hole states in 131Sn to those of single-particle states in 133Sn determined in a recent measurement of the 132Sn(d, p)133Sn reaction. We found a significant reduction of the energy splitting of the weakly bound 3p orbits compared to the well-bound 2d orbits, and that all the observed energy splittings can be reproduced remarkably well by calculations using a one-body spin-orbit interaction and a Woods–Saxon potential of standard radius and diffuseness. The observed reduction of spin-orbit splitting can be explained by the extended radial wavefunctions of the weakly bound orbits, without invoking a weakening of the spin-orbit strength.

DOI： 10.1016/j.physletb.2018.08.005

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We report on the calculation of double-β decay properties of 130Te and 136Xe within the framework of the realistic shell model. The effective shell-model Hamiltonian and Gamow-Teller transition operator are derived by way of many-body perturbation theory, in order to not to resort to an empirical quenching of the axial coupling constant g A. The results compare well with experimental data, paving the way to the calculation of the neutrinoless double-β decay nuclear matrix element for the nuclei that are currently the experimental target for the detection of this process. In this work we investigate about the perturbative properties of our approach, and the theoretical reliability of the realistic shell model.

DOI： 10.1088/1742-6596/1056/1/012012

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We have found two typographical errors in the original paper. First, the prefactor on the right-hand-side of Eq. (25) was wrong. It should be replaced by (Formula Presented). Note that all the numerical calculations were carried out using the correct prefactor and parameter. The results and conclusions of the original article remain unchanged.

DOI： 10.1103/PhysRevC.97.029901

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Background: Coherent one-particle one-hole (1p1h) excitations have given us effective insights into general nuclear excitations. However, the two-particle two-hole (2p2h) excitation beyond 1p1h is now recognized as critical for the proper description of experimental data of various nuclear responses. Purpose: The spin-flip charge-exchange reactions Ca48(p,n)Sc48 are investigated to clarify the role of the 2p2h effect on their cross sections. The Fermi transition of Ca48 via the (p,n) reaction is also investigated in order to demonstrate our framework. Methods: The transition density is calculated microscopically with the second Tamm-Dancoff approximation, and the distorted-wave Born approximation is employed to describe the reaction process. A phenomenological one-range Gaussian interaction is used to prepare the form factor. Results: For the Fermi transition, our approach describes the experimental behavior of the cross section better than the Lane model, which is the conventional method. For spin-flip excitations including the GT transition, the 2p2h effect decreases the magnitude of the cross section and does not change the shape of the angular distribution. The Δl=2 transition of the present reaction is found to play a negligible role. Conclusions: The 2p2h effect will not change the angular-distributed cross section of spin-flip responses. This is because the transition density of the Gamow-Teller response, the leading contribution to the cross section, is not significantly varied by the 2p2h effect.

DOI： 10.1103/PhysRevC.96.054608

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Interference effect of neutron capture cross section between the compound and direct processes is investigated. The compound process is calculated by resonance parameters and the direct process by the potential model. The interference effect is tested for neutron-rich 82Ge and 134Sn nuclei relevant to r-process and light nucleus 13C which is neutron poison in the s-process and produces long-lived radioactive nucleus 14C (T1/2 = 5700 y). The interference effects in those nuclei are significant around resonances, and low energy region if s-wave neutron direct capture is possible. Maxwellian averaged cross sections at kT = 30 and 300 keV are also calculated, and the interference effect changes the Maxwellian averaged capture cross section largely depending on resonance position.

DOI： 10.1051/epjconf/201716300037

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Although several analyses of the α-transfer reaction16O(6Li, d)20Ne using the distorted wave Born approximation have been performed with the aim to clarify the α-cluster structure of20Ne, they have resulted in poor information on the clustering due to insufficiency of models for the analyses. In this work we propose a precise model employing the coupled-channels Born approximation with the microscopically calculated cluster wave function to elucidate the surface manifestation of the α-particle in the ground state of20Ne. Our calculation has shown improvement of the theoretical calculation compared with that in the previous analyses. We have confirmed numerically that the angular distributed cross section at the forward angles probes only the surface region of the α-cluster wave function. The breakup effect of6Li has been investigated and concluded that only the back coupling is important for the (6Li, d) reaction.

DOI： 10.1088/1742-6596/863/1/012036

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The study of exotic nuclear structures, such as halo nuclei, is usually performed through nuclear reactions. An accurate reaction model coupled to a realistic description of the projectile is needed to correctly interpret experimental data. In this contribution, I briefly summarise the assumptions made within the modelling of reactions involving halo nuclei. I describe briefly the Continuum-Discretised Coupled Channel method (CDCC) and the Dynamical Eikonal Approximation (DEA) in particular and present a comparison between them for the breakup of 15C on Pb at 68AMeV. I show the problem faced by the eikonal approximation at low energy and detail a correction that enables its extension down to lower beam energies. A new reaction observable is also presented. It consists of the ratio between angular distributions for two different processes, such as elastic scattering and breakup. This ratio is completely independent of the reaction mechanism and hence is more sensitive to the projectile structure than usual reaction observables, which makes it a very powerful tool to study exotic structures far from stability.

DOI： 10.1088/1742-6596/724/1/012005

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Some recent activities with the microscopic effective reaction theory (MERT) on elastic, inelastic, breakup, transfer, and knockout processes are reviewed briefly. As a possible alternative to MERT, a description of elastic and inelastic scattering with the continuum particle-vibration coupling (cPVC) method is also discussed.

DOI： 10.1051/epjconf/201612206003

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Background: Direct evidence of the α-cluster manifestation in bound states has not been obtained yet, although a number of experimental studies were carried out to extract the information of the clustering. In particular in conventional analyses of α-transfer reactions, there exist a few significant problems on reaction models, which are insufficient to qualitatively discuss the cluster structure. Purpose: We aim to verify the manifestation of the α-cluster structure from observables. As the first application, we plan to extract the spatial information of the cluster structure of the Ne20 nucleus in its ground state through the cross section of the α-transfer reaction O16(Li6,d)Ne20. Methods: For the analysis of the transfer reaction, we work with the coupled-channel Born approximation (CCBA) approach, in which the breakup effect of Li6 is explicitly taken into account by means of the continuum-discretized coupled-channel method based on the three-body α+d+O16 model. The two methods are adopted to calculate the overlap function between Ne20 and α+O16; one is the microscopic cluster model (MCM) with the generator coordinate method, and the other is the phenomenological two-body potential model (PM). Results: We show that the CCBA calculation with the MCM wave function gives a significant improvement of the theoretical result on the angular distribution of the transfer cross section, which is consistent with the experimental data. Employing the PM, it is discussed which region of the cluster wave function is probed on the transfer cross section. Conclusions: It is found that the surface region of the cluster wave function is sensitive to the cross section. The present work is situated as the first step in obtaining important information to systematically investigate the cluster structure.

DOI： 10.1103/PhysRevC.93.034606

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DOI： 10.7566/jpscp.6.030060

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.7566/jpscp.6.030092

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.7566/jpscp.6.020037

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The astrophysical factor of B8(p,γ)9C at zero energy, S18(0), is determined by a three-body coupled-channels analysis of the transfer reaction B8(d,n)9C at 14.4 MeV/nucleon. Effects of the breakup channels of d and C9 are investigated with the continuum-discretized coupled-channels method. It is found that, in the initial and final channels, respectively, the transfer process through the breakup states of d and C9, its interference with that through their ground states in particular, gives a large increase in the transfer cross section. The finite-range effects with respect to the proton-neutron relative coordinate are found to be about 20%. As a result of the present analysis, S18(0)=22±6eVb is obtained, which is smaller than the result of the previous distorted-wave Born approximation analysis by about 51%.

DOI： 10.1103/PhysRevC.91.014604

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1742-6596/569/1/012023

Language：Others   Publishing type：Research paper (scientific journal)  

Extensions of the eikonal approximation to low energy (20 MeV/nucleon typically) are studied. The relation between the dynamical eikonal approximation (DEA) and the continuum-discretized coupled-channels method with the eikonal approximation (E-CDCC) is discussed. When Coulomb interaction is artificially turned off, DEA and E-CDCC are shown to give the same breakup cross section, within 3% error, of C15 on Pb208 at 20 MeV/nucleon. When the Coulomb interaction is included, the difference is appreciable and none of these models agrees with full CDCC calculations. An empirical correction significantly reduces this difference. In addition, E-CDCC has a convergence problem. By including a quantum-mechanical correction to E-CDCC for lower partial waves between C15 and Pb208, this problem is resolved and the result perfectly reproduces full CDCC calculations at a lower computational cost.

DOI： 10.1103/PhysRevC.90.034617

Language：Others   Publishing type：Research paper (scientific journal)  

We discuss how to extract an electric dipole (E1) breakup cross section σ(E1) from one-neutron removal cross sections measured at 250 MeV/nucleon by using 12C and 208Pb targets, σC-1n and σPb-1n, respectively. It is shown that, within about 5% error, σ(E1) can be obtained by subtracting ΓσC-1n from σPb-1n, as assumed in preceding studies. However, for the reaction of weakly bound projectiles, the scaling factor Γ is found to be about twice as large as that usually adopted. As a result, we obtain a 13-20% smaller σ(E1) of 31Ne at 250 MeV/nucleon than extracted in a previous analysis of experimental data. By compiling the values of Γ obtained for several projectiles, Γ = (2.30 ± 0.41) exp(-Sn) + (2.43 ± 0.21) is obtained, where Sn is the neutron separation energy. The target mass-number dependence of the nuclear parts of the one-neutron removal cross section and the elastic breakup cross section is also investigated. © The Author(s) 2014.

DOI： 10.1093/ptep/ptu063

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1051/epjconf/20146603031

Language：Others   Publishing type：Research paper (scientific journal)  

The astrophysical factor of the 8B(p, γ)9C reaction at zero energy, S18(0), is determined from three-body model analysis of 9C breakup processes. The elastic breakup 208Pb(9C,p8B)208Pb at 65 MeV/nucleon and the one-proton removal reaction of 9C at 285 MeV/nucleon on C and Al targets are calculated with the continuum-discretized coupled-channels method (CDCC) and the eikonal reaction theory (ERT), respectively. As a result of the present analysis, S18(0) extracted from the two reactions shows good consistency, in contrast to in the previous studies. © 2013 Springer-Verlag Wien.

DOI： 10.1007/s00601-012-0580-2

Language：Others   Publishing type：Research paper (scientific journal)  

Tensor correlations in 4He were studied via the (p, dp) reaction at the incident energy of 392 MeV with a focus on spin configurations of correlated pn pairs in 4He at high relative momenta (Prelcor). The preliminary results show that the correlated pn pair at Prelcor = 310 MeV/c predominantly has the channel spin S = 1, which is consistent with the characteristics of tensor correlations. © 2013 Springer-Verlag Wien.

DOI： 10.1007/s00601-013-0611-7

Language：Others   Publishing type：Research paper (scientific journal)  

The astrophysical factor of 8B(p,γ)9C at zero energy, S 18(0), is determined from three-body model analysis of 9C breakup processes. The elastic breakup reaction 208Pb(9C,p8B)208Pb at 65 MeV/nucleon and the one-proton removal reaction of 9C at 285 MeV/nucleon on C and Al targets are calculated with the continuum-discretized coupled-channels method (CDCC) and the eikonal reaction theory (ERT), respectively. The asymptotic normalization coefficient (ANC) of 9C in the p-8B configuration, Cp8B9C, extracted from the two reactions shows good consistency, unlike in previous studies. As a result of the present analysis, S18(0)=66±10eVb is obtained. © 2012 American Physical Society.

DOI： 10.1103/PhysRevC.86.022801

Language：Others   Publishing type：Research paper (scientific journal)  

Subbarrier α transfer reaction 13C(6Li, d) 17O(6.356 MeV, 1/2+) at 3.6 MeV is analyzed with an α + d +13C three-body model, and the asymptotic normalization coecient (ANC) for α+13C → 17O(6.356 MeV, 1/2+), which essentially determines the reaction rate of 13C(α, n)16O, is extracted. Breakup eects of 6Li in the initial channel and those of 17O in the nal channel are investigated with the continuum-discretized coupled-channels method (CDCC). The former is found to have a large back-coupling to the elastic channel, whereas the latter turns out to be signicantly small. The transfer cross section calculated with Born approximation to the transition operator, including breakup states of 6Li, gives (C17O *α13C)2 = 1.03 ± 0.29 fm-1. This result is consistent with the value obtained by the previous DWBA calculation.

DOI： 10.1143/PTP.125.1193